Particulate strengthened alloy articles and methods of forming

ABSTRACT

An article and a method for forming the article are presented. The article includes a material comprising a metal matrix and a first population of particulate phases disposed macroscopically non-uniformly within the matrix. The particulate phases include an oxide phase. Further embodiments include articles, such as turbomachinery components, fasteners, and pipes, for example, and methods for forming the articles.

BACKGROUND

The invention relates generally to nano structured ferritic alloys. Moreparticularly, the invention relates to articles formed of nanostructuredferritic alloys having non-uniformly distributed dispersions, andmethods of forming thereof.

Gas turbines operate in extreme environments, exposing the turbinecomponents, especially those in the turbine hot section, to highoperating temperatures and stresses. In order for the turbine componentsto endure these conditions, they are manufactured from a materialcapable of withstanding these severe conditions. As material limits arereached, one of two approaches is conventionally used in order tomaintain the mechanical integrity of hot section components. In oneapproach, cooling air is used to reduce the part's effectivetemperature. In a second approach, the component size is increased toreduce the stresses. However, these approaches can reduce the efficiencyof the turbine and increase the cost.

In certain applications, superalloys have been used in these demandingapplications because they maintain their strength at up to 90% of theirmelting temperature and have excellent environmental resistance.Nickel-based superalloys, in particular, have been used extensivelythroughout gas turbine engines, e.g., in turbine blade, nozzle, wheel,spacer, disk, spool, blisk, and shroud applications. In some lowertemperature and stress applications, steels may be used for turbinecomponents. However, use of conventional steels is often limited in hightemperature and high stress applications because of not meeting thenecessary mechanical property requirements and/or design requirements.

Nanostructured ferritic alloys (NFA) are an emerging class of alloysthat are of considerable interest for the gas turbine rotors. Thesealloys (NFAs) exhibit exceptional high temperature properties, thoughtto be derived from nanometer-sized oxide clusters that precipitateduring hot consolidation following a mechanical alloying step. Theseoxide clusters are present at high temperatures, providing a strong andstable microstructure during service. Moreover, unlike many nickel-basedsuperalloys, that require the cast and wrought (C&W) process to befollowed to obtain necessary properties, NFAs are manufactured via adifferent processing route that requires fewer melting steps.

While NFAs yield enhanced tensile and creep properties compared toconventional steels, additional benefits are sought for rotorapplications. It should be noted that for the heavy duty gas turbinerotors, critical mechanical property requirements change from the boreto the rim of a wheel. For example, the bore is limited by burststrength, and hence would require a higher ultimate tensile strength,and the rim is limited by a material's creep life.

Accordingly, it is desirable to have a graded alloy article thatexhibits improved mechanical integrity over various regions (locations)of the article with a proper balance of mechanical properties.

BRIEF DESCRIPTION

In one embodiment, an article is provided. The article includes amaterial comprising a metal matrix and a first population of particulatephases disposed macroscopically non-uniformly within the matrix. Theparticulate phases include an oxide phase. Further embodiments includearticles, such as turbomachinery components, fasteners, and pipes, forexample.

One embodiment is a turbomachinery component. The component includes aradially symmetrical body having an inner surface proximate to a centerof the body and an outer surface distal to the center of the body. Thebody includes a material comprising a metal matrix and a firstpopulation of particulate phases. The metal matrix includes iron andchromium. The first population of particulate phases includes an oxidephase that includes titanium and yttrium, and has a median size lessthan about 20 nanometers. A concentration of the first population of theparticulate phases at the inner surface is less than a concentration ofthe first population of the particulate phases at the outer surface. Theconcentration of the first population of the particulate phases at theinner surface is in a range from about 0.1 volume percent to about 2volume percent, and the concentration at the outer surface is in a rangefrom about 0.7 volume percent to about 3 volume percent.

In one embodiment, a method includes joining a first compositioncomprising a first oxygen concentration to a second composition having asecond oxygen concentration to form a material. The second oxygenconcentration is different from the first oxygen concentration. Thematerial includes a metal matrix and a first population of particulatephases disposed macroscopically non-uniformly within the matrix. Theparticulate phases include an oxide phase. The material is processed toprovide an article.

In one embodiment, a method of forming a turbomachinery component isprovided. The method includes steps of milling a first powder includingiron and chromium in the presence of an oxide until the oxide is atleast partially dissolved into the alloy powder, and thus forming afirst composition having a first oxygen concentration; and milling asecond powder including iron and chromium in the presence of an oxideuntil the oxide is at least partially dissolved into the alloy powder,thus forming a second composition having a second oxygen concentrationthat is greater than the first oxygen concentration. The powder havingthe first composition is disposed in a first region of a container, andthe powder having the second composition is disposed in a second regionof the container. These powders are consolidated to thereby join thefirst and second compositions at a temperature to precipitate an oxidephase comprising titanium and yttrium within a matrix comprising ironand chromium. The first region of the container and the second region ofthe container respectively correspond to an inner surface and an outersurface of a radially symmetrical body of the turbomachinery component.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings.

FIG. 1 is a schematic representation of an article, in accordance withone embodiment of the present invention;

FIG. 2 is a schematic representation of an article, in accordance withone embodiment of the present invention;

FIG. 3 is a schematic representation of a top-down cross-section of aturbomachinery component, in accordance with one embodiment of thepresent invention;

FIG. 4 is a schematic representation of a top-down cross-section of aturbomachinery component, in accordance with one embodiment of thepresent invention;

FIG. 5 schematically represents a container for forming an article, inaccordance with one embodiment of the present invention.

DETAILED DESCRIPTION

Embodiments of the invention described herein address the notedshortcomings of the state of the art. One or more specific embodimentsof the present invention will be described below. In an effort toprovide a concise description of these embodiments, all features of anactual implementation may not be described in the specification. Itshould be appreciated that in the development of any such actualimplementation, as in any engineering or design project, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be appreciated that such a developmenteffort might be complex and time consuming, but would nevertheless be aroutine undertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the presentinvention, the articles “a,” “an,” and “the,” are intended to mean thatthere are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.Moreover, the use of “top,” “bottom,” “above,” “below,” and variationsof these terms is made for convenience, but does not require anyparticular orientation of the components unless otherwise stated.

All ranges disclosed herein are inclusive of the endpoints, and theendpoints are combinable with each other. The terms “first,” “second,”and the like as used herein do not denote any order, quantity, orimportance, but rather are used to distinguish one element from another.

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it may be about related. Accordingly, a value modifiedby a term such as “about” is not limited to the precise value specified.In some instances, the approximating language may correspond to theprecision of an instrument for measuring the value.

Embodiments of the invention provide an article including a metal matrixand a first population of particulate phases that is macroscopicallynon-uniformly disposed within the metal matrix. The metal matrix mayinclude nickel, iron, chromium, aluminum, cobalt, titanium, or acombination thereof. In one embodiment, the metal matrix includes aniron-containing alloy. The first population of particulate phasesincludes an oxide phase.

As used herein, “macroscopically non-uniform disposition” refers toheterogeneous dispersion of particulate phases over a length scale of atleast 0.5 centimeter of the metal matrix. That is, a concentration ofthe particulate phases in a first portion of the article varies from aconcentration of the particulate phases in a second portion, wherein theportions often extend over a length scale of at least about 0.5centimeter. In some embodiments, the portions may extend to a lengthscale of up to about 200 centimeters. In certain embodiments, theportions may extend to a length scale of up to about 100 centimeters. Asused herein, “disposed within the matrix” includes the dispersion of theparticulate phases in the grains and grain boundaries of the matrix.

Some embodiments provide an article including a nanostructured ferriticalloy (NFA). Typically a nano structured ferritic alloy includes aniron-containing alloy matrix that is strengthened by nanofeaturesdisposed in the matrix. The concentration of iron in the alloy matrixmay be greater than about 50 weight percent. In one embodiment, the ironcontent in the alloy matrix is greater than about 70 weight percent. Inone embodiment, the alloy matrix is in the form of the ferriticbody-centered cubic (BCC) phase. As used herein, the term “nanofeatures”means particles of matter having a largest dimension less than about 20nanometers in size. The nanofeatures of an NFA may have any shape,including, for example, spherical, cuboidal, lenticular, and othershapes. The nanofeatures used herein are typically in-situ formed in theNFA by the dissolution of at least a portion of the initial added oxideand the precipitation of nanometer sized particles of a modified oxidethat can serve to pin the alloy structure, thus providing enhancedmechanical properties.

FIG. 1 illustrates an article 10 in accordance with some embodiments ofthe present invention. The article 10 includes a nano structuredferritic alloy having a first population of particulate phasesmacroscopically non-uniformally disposed within the article, forexample, from a first surface 12 to a second surface 14. In someembodiments, the article 10 has graded concentration of the firstparticulate phases from the first surface 12 towards the second surface14. The gradation may be continuous or step wise.

In the illustrated embodiment, the article 10 includes a first region 18extending from the first surface 12 to a predetermined surface 16, and asecond region 20 extending from a second surface 14 to the predeterminedsurface 16. The first region 18 includes a first concentration of thefirst particulate phases, and the second region 20 includes a secondconcentration of the first particulate phases, where the firstconcentration of the first particulate phases in the first region 18 isnot equal to the second concentration of the first particulate phases inthe second region 20. In one embodiment, each of the first concentrationin the first region 18 and the second concentration in the second region20 is independently within a range from about 0.1 volume percent toabout 5 volume percent.

In some embodiments, the article 10 may have more than two regions,wherein adjacent regions have different concentration of the firstparticulate phases. For example, the article 10 may have at least threeregions, as illustrated in FIG. 2, with an intermediate region 22extending from the predetermined surface 16 to another predeterminedsurface 26. The intermediate region 22 is disposed between the firstregion 18 and the second region 20. The concentration of the firstparticulate phases in the intermediate region 22 may be different fromthe first concentration of the first particulate phases in the firstregion 18 and the second concentration of the first particulate phasesin the second region 20. In some embodiments, the concentration of thefirst particulate phases in the intermediate region 22 has a valuebetween the first concentration and the second concentration. Thearticle 10 may have a number of intermediate regions between the firstregion 18 and the second region 20. In one embodiment, the concentrationof the first particulate phases in each intermediate region is betweenthe concentrations of the particulate phases in adjacent regions. Theconcentrations of the first particulate phases may increase or decreasefrom the first region 18 towards the second region 20. In someembodiments, the alternate regions may have a same concentration of thefirst particulate phases. It should be noted herein that although thebelow material details are discussed with reference to FIGS. 1 and 2,the details are also equally applicable to the embodiment of FIGS. 3 and4.

A metal matrix (may also be referred to as alloy matrix) of the NFAincludes iron and chromium. Chromium is important for both phasestability and oxidation and/or corrosion resistance, and may thus beincluded in the NFA in amounts of at least about 5 weight percent.Amounts of up to about 30 weight percent may be included. In oneembodiment, chromium is present in a range from about 9 weight percentto about 14 weight percent of the alloy. In some embodiments, the alloymay have titanium and yttrium. The titanium and yttrium may be presentin the metallic or alloy form as a part of the matrix of the alloy, ormay be present in the particulate phases of the alloy. They may play arole in the formation of the oxide nanofeatures, as described herein. Insome embodiments, the titanium is present in a range from about 0.1weight percent to about 2 weight percent, and yttrium from about 0.1weight percent to about 3 weight percent of the alloy. In addition, thealloy may include one or more of vanadium, molybdenum, manganese,tungsten, niobium, silicon or tantalum.

The first population of particulate phases may be the above-describednanofeatures, providing enhanced tensile and creep properties to thealloy. The nanofeatures of the first population have a median size lessthan about 20 nanometers (nm). In some embodiments, the particulatephases of the first population have a median size less than about 15 nm.In certain embodiments, the median size of the particulate phases isless than about 10 nm. In some embodiments, the first population ofparticulate phases may include a complex oxide. A “complex oxide” asused herein is an oxide phase that includes more than one non-oxygenelements. The complex oxide may be a single oxide phase having more thanone non-oxygen elements such as, for example, ABO (where A, B signifynon-oxygen elements); or may be a mixture of multiple simple oxidephases (having one non-oxygen element) such as, for exampleA_(x)B_(y)O_(z), where x, y, z denote the relative molar ratios of theelements in the mixture. The examples included here do not account forcharge balance, and hence will include the oxides of elements ofdifferent valencies and deviations from stoichiometry.

In one embodiment, an oxide material may be added to the alloy matrix,and processed to precipitate nanofeatures of the first population. Atleast a part of the added oxide phase may be dissolved in the alloystructure and precipitated as the nanofeatures. In one embodiment, theprecipitated oxide in the NFA may include transition metals (forexample, titanium and yttrium) present in the starting materials and themetallic element(s) of the initial oxide addition.

In one embodiment, the particulate phases of the first populationinclude at least two elements from the group of yttrium, titanium,aluminum, zirconium, molybdenum, silicon, hafnium, magnesium, tungsten,and tantalum. The particulate phases may include a combination of two ormore simple oxides; a combination of one or more simple oxide and one ormore complex oxides; or a combination of multiple different complexoxides. In a particular embodiment, the particulate phases of the firstpopulation include a complex oxide with a single phase including morethan one non-oxygen element, such as for example, a yttrium titaniumoxide; a yttrium titanium silicon oxide; an aluminum titanium oxide; amagnesium titanium oxide; a zirconium titanium oxide; hafnium titaniumoxide; a magnesium zirconium oxide; zirconium hafnium oxide; a yttriumzirconium oxide; a yttrium magnesium oxide; a yttrium zirconium titaniumoxide; or a yttrium aluminum titanium oxide.

It should be noted here that the use of the plural term “phases” in thiscontext does not necessitate that multiple phase compositions arepresent within a population; rather, “phases” is used to denote thepresence of a plurality of particles in the matrix, which may or may notbe of homogeneous composition.

In some embodiments, the article 10 (FIGS. 1 and 2) further includes asecond population of particulate phases within the alloy matrix. Theaddition of the second particulate phases may enhance the tensile andcreep properties of the NFA, while maintaining a desirable level ofductility. The second population of particulate phases may have adifferent particle size distribution than that of the first populationof the particulate phases. The second population of the particulatephases may have a median particulate size in a range from about 25 nm toabout 10 microns. In one embodiment, the second population ofparticulate phases has a median size in a range from about 50 nm toabout 3 microns.

The second population of the particulate phases may be distributeduniformly or non-uniformly within the article 10. In one embodiment, thesecond population of the particulate phases is disposed macroscopicallynon-uniformly within the alloy matrix. For example, as discussed withrespect to the first population of particulate phases in previousembodiments, a concentration of the second particulate phases in eachintermediate region is between the concentrations of the particulatephases in adjacent regions (FIG. 2). The concentrations of theparticulate phases may increase or decrease from the first region 18towards the second region 20. The concentrations of the secondpopulation of particulate phases in each region of the article mayindependently be within a range from about 1 volume percent to about 15volume percent, and more particularly, from about 1 volume percent toabout 6 volume percent of the alloy. In a particular embodiment, theconcentration the population of particulate phases (including both firstpopulation and second population) in each region of the article is in arange from about 2 volume percent to about 6 volume percent in thealloy.

In some embodiments, the second population may include an oxide, aboride, a carbide, a nitride, or a combination thereof. An oxide may beadded to the alloy during processing to further strengthen the alloy. Inone embodiment, the concentration of total oxygen in the alloy is in arange from about 0.1 weight percent to about 0.6 weight percent of thealloy. In some embodiments, a precipitated particulate phase of thesecond population is an intermetallic phase. Non-limiting examples ofthe intermetallic phase may include a Laves phase, a Mu phase, aZ-phase, and a Ni₃M structure. Various features and methods of formingan alloy having a precipitated first population of particulate phasesand an added second population of particulate phases are described indetails in previously filed patent application Ser. Nos. 13/931,108 and14/074,768.

Referring to FIGS. 1 and 2 again, the article 10 may be a turbomachinerycomponent, in some embodiments. In other embodiments, the article 10 mayalso be applicable for any other applications involving operation at ahigh temperature, such as a fastener, a pipe etc, as well as a lowtemperature, such as pipes and disks for transporting oils and gases. Inone embodiment, the article 10 is a turbine wheel. In anotherembodiment, the article 10 is a turbine spacer.

As discussed previously, critical mechanical properties change from thebore to the rim of a turbine wheel. For example, the bore is limited byburst strength, and hence would require a higher ultimate tensilestrength, and the rim is limited by a material's creep life. Generally,increasing the concentration of the oxide nanofeatures results inimproved tensile properties as required for the wheel's bore andimproved creep properties for the wheel's rim. However, theconcentration of the oxide nanofeatures is limited to a nominal amountbecause of a reduction in the ductility of the material, which is alarger concern at the bore than the rim.

Some embodiments of the present invention provide a turbomachinerycomponent having macroscopically non-uniform dispersion of a firstpopulation of the particulate phases that includes an oxide phase, toprovide required mechanical properties in particular locations orregions, for example at a bore and a rim of the turbomachinerycomponent. FIG. 3 illustrates a top-down cross-section of aturbomachinery component 30 having a radially symmetrical body, forexample a wheel or a spacer. The center of the radially symmetriccomponent 30 is located at 31. The component 30 includes ananostructured ferritic alloy (NFA) as described herein. In theillustrated embodiment, the turbomachinery component 30 includes aninner surface 32 (bore) proximate to a center 31 of the radiallysymmetrical body of the component 30, and an outer surface 36 (rim)distal to the center 31 of the component 30. The inner surface 32 of thecomponent 30 defines a hole concentric with the radially symmetricalbody. In one embodiment, a first concentration of the first particulatephases in the alloy at the inner surface 32 is less than a secondconcentration of the first particulate phases at the outer surface 36 ofthe wheel. In one embodiment, the wheel 30 includes a nanostructuredferritic alloy having a graded concentration of the first particulatephases from the inner surface 32 to the outer surface 36.

In some embodiments as illustrated in FIG. 4, the turbomachinerycomponent 30 has a first region 38 extending from the inner surface 32to a predetermined surface 34, and a second region 40 extending from theouter surface 36 to the predetermined surface 34. In one embodiment, thefirst region 38 and the second region 40 include the same composition ofthe NFA matrix and the concentration of the first particulate phases inthe alloy varies. A first concentration of the first particulate phasesin the first region 38 is less than the second concentration of thefirst particulate phases in the second region 40 of the component 30.

In some embodiments, the first concentration of the first particulatephases in the first region 38 is in a range from about 0.1 volumepercent to about 2 volume percent of the alloy, and the secondconcentration of the first particulate phases in the second region 40 isin a range from about 0.7 volume percent to about 3 volume percent ofthe alloy. In some embodiments, the component 30 may have a number ofintermediate regions disposed between the first region 38 and the secondregion 40, as discussed in previous embodiments. In certain embodiments,the component 30 may include a graded nanostructured ferritic alloy i.e.a nanostructured ferritic alloy having a gradually increasingconcentration of the first particulate phases from the inner surface 32to the outer surface 36 (FIG. 3).

By tailoring the concentration of the first particulate phases (thatincludes an oxide phase) in the alloy matrix, desired mechanicalproperties in specific locations of a component can be achieved. Forexample, a wheel may have a low concentration of an oxide phase near thebore region to provide good ultimate tensile strength and ductility toresist burst, and a high concentration of the oxide phase near the rimregion to enhance creep resistance. Typically, these location specificproperties can be achieved by using multiple alloys. However, use ofthese multiple dissimilar chemistry alloys results in inter-diffusion atthe joining surface. This inter-diffusion may adversely affectmechanical properties during the service of the component, and thusreduce service life. Use of a consistent alloy matrix throughout thewheel with varying concentration of an oxide phase enables locationspecific properties to be achieved while maintaining the same matrix toeliminate diffusion issues and property changes with time.

Some embodiments provide a method of forming an article. The methodincludes joining a first composition and a second composition to form anarticle. The first composition and the second composition may be joinedthrough one or more than one intermediate composition disposed betweenthem. In one embodiment, a number of compositions may be joined byjoining one composition with an adjacent composition. The firstcomposition may have a first oxygen concentration and the secondcomposition may have a second oxygen concentration that is differentfrom the first oxygen concentration. The resulting article includes ametal matrix and a first population of particulate phases disposedmacroscopically non-uniformly within the article. The first populationof particulate phases includes an oxide phase. In certain embodiments,the resulting material includes a NFA.

Oxygen concentration, as used herein, refers to a total oxygenconcentration of a composition, which may include dissolved oxygen andany other oxygen that is present in the form of an oxide or in otherphases present in the NFA.

The method of forming a composition of NFA may include forming an alloypowder and consolidating the powder. The alloy powder may be formed byany of the methods known in the art. A process of forming the alloypowder may start from melting starting materials such as, for example,iron and chromium to form an initial melt. A vacuum induction meltingprocess may be conveniently used to melt the starting material. Themelted material may be atomized to form the alloy powder that can bemilled along with an added oxide material to form a milled alloy powder.In one embodiment, the oxide material includes yttria, zirconia, hafnia,alumina, silica, magnesia, or a combination thereof. Usually, the milledalloy powder may be processed by consolidating at a temperature toprecipitate a desired concentration of the first population of theparticulate phases having an oxide phase with a desired size. Suitableprocessing techniques may include isothermal forging, hot isostaticpressing (HIP), extrusion, or a combination thereof. In one embodiment,the processing of the milled alloy powder includes hot isostaticpressing (HIP). At least some of the added oxide is dissolved into thealloy matrix during powder attrition, and precipitates in the formationof the aforementioned nanofeatures when the powder is raised to atemperature during the consolidation process. In any given instance ofthis method, the amount of added oxide that dissolves can be less than amajority, or substantially all of the added oxide, depending onprocessing parameters and materials selected. In one embodiment, thefirst particulate phases of complex oxides may precipitate during theconsolidation step. In one embodiment, a second population ofparticulate phases may be established by adding and mixing an oxide tothe milled alloy powder as described in patent application Ser. Nos.13/931,108 and 14/074,768.

An article, for example the turbomachinery component 30 (FIG. 4) may bemanufactured using several techniques. The first region 38 includes thefirst composition, and the second region 40 includes the secondcomposition. The first composition and the second composition may beformed by the process as discussed above. The formation of the firstcomposition includes milling an alloy powder in presence of a firstamount of an oxide, and the formation of the second composition includesmilling the alloy powder in presence of a second amount of the oxide.The alloy powders are milled until the oxide is at least partiallydissolved into the alloy powder. In any given instance of this method,the amount of added oxide that dissolves can be less than the majority,or a majority, or substantially all of the added oxide, depending onprocessing parameters and materials selected.

In some embodiments, the first composition and the second compositionare present in milled alloy powder form. Referring to FIG. 5, the methodincludes steps of disposing the first composition in a first region 52of a container 50 (for example, HIP can), and disposing a secondcomposition in a second region 54 of the container 50. The container 50is cylindrical about an axis 60. The first region 52 of the container 50proximate to the axis 60, is defined by a first surface 56 that maycorrespond to the predetermined surface 34 of the component 30 of FIG.4. Further, a portion of the first region 52 of the container 50 maycorrespond to the first region 38 of the component 30. A second surface58 of the container 50 may correspond to the second surface 36 (FIG. 4),i.e. the second region 54 of the container 50 may correspond to thesecond region 40 of the component 30 (FIG. 4). The two alloy powders maybe separated by a metallic sheet (for example, baffle) at the time ofdisposing the compositions in the container 50. The method furtherincludes simultaneously consolidating the milled alloy powders of thefirst composition and the second composition, and thereby joining thetwo consolidated compositions to form a solid feedstock (defined below)having a first portion and a second portion corresponding to the firstand second regions 52 and 54 of the container 50. The metallic sheet canbe removed from the container before the consolidation step to allow thetwo compositions to join during the HIP process. In certain embodiments,the two alloy powders are consolidated by HIP followed by forging orextrusion. The consolidation process may be performed at a temperatureto precipitate a first concentration and a second concentration of anoxide phase including titanium and yttrium in the first region 52 andthe second region 54 of the container, respectively. In certainembodiments, the first concentration of the oxide phase in the firstregion 52 is less than the second concentration of the oxide phase inthe second region 54.

The container 50 used to consolidate the NFA alloy, may not have a borehole as shown in FIGS. 3 and 4 defined by the inner surface 32 of theradially symmetrical body of the component 30. The bore hole can bemachined in a first portion of the resulting solid feedstock aftercompletion of the processing of the NFA. As used herein, the firstportion of the solid feedstock corresponds to the first composition thatforms the inner surface 32 of the first region 38 of the component 30after the bore hole is machined.

In some embodiments, the first composition and the second compositionare present in form of solid feedstock. Solid feedstock refers to asolid continuous structure that does not include a powder form. Themilled alloy powders of first composition and the second composition areseparately consolidated in desired shapes to form solid feedstocks. Forexample, referring to FIG. 5, a first (i.e., inner) feedstockcorresponding to the first region 52 including the first composition anda second feedstock corresponding to the second region 54 including thesecond composition are manufactured beforehand, and then joined. Asdiscussed, a bore hole can be machined in the first feedstock includingthe first composition. In these embodiments, joining may be performed bywelding, co-extruding, solid state joining, diffusion bonding, shrinkfitting, or a combination thereof.

In some embodiments, at least one of the first composition or the secondcomposition is in form of solid feedstock, and the other composition isin powder form. In one example, the first composition may be a solidfeedstock that can be placed in the first region 52 of the container 50,and the second composition may be a powder that can be disposed in thesecond region 54 (i.e. around the solid feedstock of the firstcomposition) of the container 50. In another example, the secondcomposition may be a solid feedstock of having a hollow spacesubstantially in the middle, which can be placed in the second region 54of the container 50. The first composition may be a powder that can bedisposed in the first region 52 (i.e., the hollow space of the solidfeedstock). In these embodiments, the method further includesconsolidating the powder of the second composition and thereby bondingthe second composition to the first composition. In some embodiments,the first and the second compositions are processed by HIP followed byforging. In some embodiments, the first composition and the secondcompositions are processed by HIP and extrusion. Examples of othersuitable bonding techniques include co-extrusion, and spray techniquessuch as cold spray, thermal spray, and plasma spray.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

1. An article, comprising: a material comprising a metal matrix and afirst population of particulate phases disposed macroscopicallynon-uniformly within the matrix, the particulate phases comprising anoxide phase.
 2. The article of claim 1, wherein the matrix comprisesnickel, iron, chromium, aluminum, cobalt, titanium, or a combinationthereof.
 3. The article of claim 1, wherein the matrix comprises ironand chromium.
 4. The article of claim 1, wherein the oxide phasecomprises aluminum, yttrium, magnesium, molybdenum, zirconium, silicon,titanium, hafnium, tungsten, tantalum, or a combination thereof.
 5. Thearticle of claim 1, wherein the oxide phase comprises titanium andyttrium.
 6. The article of claim 1, wherein the first population ofparticulate phases has a median size less than about 20 nm.
 7. Thearticle of claim 1, wherein the first population of particulate phaseshas a median size less than about 10 nanometers.
 8. The article of claim1, further comprising a second population of particulate phases disposedwithin the matrix, wherein the second population of particulate phaseshas a different size distribution from the size distribution of thefirst population of particulate phases.
 9. The article of claim 8,wherein the second population of particulate phases is distributedmacroscopically non-uniformly within the matrix.
 10. The article ofclaim 8, wherein the second population of particulate phases comprisesan intermetallic compound.
 11. The article of claim 8, wherein thesecond population of particulate phases comprises an oxide, a boride, acarbide, a nitride, or combinations thereof.
 12. The article of claim 8,wherein the second population of particulate phases has a median size ina range from about 25 nm to about 10 microns.
 13. The article of claim1, wherein a first concentration of the first population of theparticulate phases in a first region of the article is not equal to asecond concentration of the first population of the particulate phasesin a second region of the article, and wherein each of the firstconcentration and second concentration is independently within a rangefrom about 0.1 volume percent to about 5 volume percent.
 14. The articleof claim 13, wherein at least one intermediate region is disposedbetween the first region and the second region, and wherein theconcentration of the first population of the particulate phases in theat least one intermediate region has a value that is between the firstconcentration and the second concentration.
 15. The article of claim 13,wherein the article is a turbomachinery component, a fastener or a pipe.16. The article of claim 15, wherein the article is a wheel or a spacer.17. The article of claim 16, wherein a first region comprises an innersurface of the wheel or spacer, and a second region comprises an outersurface of the wheel or spacer, and wherein a first concentration of thefirst population of the particulate phases at the inner surface is lessthan a second concentration of the first population of the particulatephases at the outer surface.
 18. The article of claim 17, wherein thefirst concentration is in a range from about 0.1 volume percent to about2 volume percent, and the second concentration is in a range from about0.7 volume percent to about 3 volume percent.
 19. A turbomachinerycomponent, comprising: a radially symmetrical body comprising an innersurface proximate to a center of the body and an outer surface distal tothe center of the body; wherein the body comprises a material comprisinga metal matrix, the matrix comprising iron and chromium; a firstpopulation of particulates having a median size less than about 20nanometers, the particulate phases comprising an oxide phase, the oxidephase comprising titanium and yttrium, wherein a concentration of thefirst population of the particulate phases at the inner surface is lessthan a concentration of the first population of the particulate phasesat the outer surface, and wherein the concentration of the particulatephases at the inner surface is in a range from about 0.1 volume percentto about 2 volume percent, and the concentration of the particulatephases at the outer surface is in a range from about 0.7 volume percentto about 3 volume percent.
 20. A method comprising: joining a firstcomposition comprising a first oxygen concentration to a secondcomposition having a second oxygen concentration, the second oxygenconcentration different from the first oxygen concentration, to form amaterial comprising a metal matrix and a first population of particulatephases disposed macroscopically non-uniformly within the matrix, theparticulate phases comprising an oxide phase.
 21. The method of claim20, further comprising milling an alloy powder comprising iron andchromium in the presence of a first amount of an oxide until the oxideis at least partially dissolved into the alloy powder, thus forming thefirst composition.
 22. The method of claim 20, further comprisingmilling an alloy powder comprising iron and chromium in the presence ofa second amount of an oxide until the oxide is at least partiallydissolved into the alloy powder, thus forming the second composition.23. The method of claim 20, wherein the first composition, the secondcomposition, or both the first composition and the second composition,are powder, and wherein joining further comprises consolidating thepowder.
 24. The method of claim 23, wherein both the first compositionand the second composition are powder.
 25. The method of claim 24,further comprising: disposing powder comprising the first composition ina first region of a container; disposing powder comprising the secondcomposition in a second region of the container; and consolidating thepowders and thereby joining the first and second compositions.
 26. Themethod of claim 20, further comprising heating the first composition,the second composition, or the material to form the first population ofparticulate phases.
 27. The method of claim 20, further comprisingestablishing a second population of particulate phases within thematrix, the second population of particulate phases having a median sizein a range from about 25 nm to about 10 microns.
 28. The method of claim20, wherein the first composition and the second composition are solidfeedstock, and wherein joining comprises co-extruding, welding,solid-state joining, diffusion bonding, shrink fitting, or a combinationthereof.
 29. The method of claim 23, wherein the first composition is asolid feedstock and the second composition is a powder, and whereinjoining comprises consolidating the powder and bonding the firstcomposition to the second composition.
 30. A method, comprising: millinga first powder comprising iron and chromium in the presence of an oxideuntil the oxide is at least partially dissolved into the alloy powder,thus forming a first composition having a first oxygen concentration;milling a second powder comprising iron and chromium in the presence ofan oxide until the oxide is at least partially dissolved into the alloypowder, thus forming a second composition having a second oxygenconcentration that is greater than the first oxygen concentration;disposing powder comprising the first composition in a first region of acontainer; disposing powder comprising the second composition in asecond region of the container; and consolidating the powders andthereby joining the first and second compositions at a temperature toprecipitate an oxide phase comprising titanium and yttrium within amatrix comprising iron and chromium; wherein the first region of thecontainer and the second region of the container respectively correspondto an inner surface and an outer surface of a radially symmetrical bodyof a turbomachinery component.